Seam rows are the stitching that form rows to hold the fabric of caps together. Seam rows are visible right next to the joints of the panels as well as on the brim, where the functionality is to attach the cloth to the hard material that is underneath. It makes the fabric stay in place and prevents it to become wrinkled.
Here in Sweden, during the late '90s, rumour had it that a cap wasn't considered authentic if it didn't have eight seam rows on the brim. What kind of authentic? If a Yankees cap had seven seam rows or less, did it mean that the cap was fake, i.e. a counterfeit? Strangely enough, yes! That was of course not true, but people followed it like a religion. Today, we know it was just a myth, and that the seams are mainly a question of design with an actual functionality. When we produce caps in our factory, we have to specify how many rows of seams we prefer.